1. Field of the Invention
The present invention relates to methods of forming strip materials having inflatable chambers between two heat sealable films, and of subsequently filling the chambers with gas and sealing them to form cushioning material.
2. Description of the Prior Art
U.S. Pat. Nos. 3,660,189 and 3,868,285 describe an elongate strip material which is formed by fusing together two flexible heat sealable films in discrete areas to define a plurality of chambers between the films with each chamber having an inlet opening. The strip material is shipped to the site of its intended use, and is then inflated and sealed to form air cushioning material. The use of this strip material and method reduces bulk handling problems and the costs of shipping air which would otherwise result if the strip material were inflated and sealed at a central production facility and was then shipped in an inflated condition to the site of its intended use. The chambers formed prior to inflation in the strip material of U.S. Pat. Nos. 3,660,189 and 3,868,285, however, extend transversely nearly across the strip material. Each chamber has at least one end which is open across the entire width of the chamber to provide the inlet opening and is positioned adjacent a longitudinal edge of the strip material. The strip material is moved to sequentially position the open ends of the chambers adjacent to a nozzle through which air flows to inflate the chambers, and the strip material must then be extensively sealed both to seal across the open ends of the chambers, and to divide the chambers longitudinally of the strip material into smaller chambers of a more suitable size. Because of the large number of seals that must be made, the strip material requires a filling and sealing device that is more complex and expensive than might be desired for use by a small manufacturing facility. Also, sealing across the full width of the inflated chambers may causes wrinkles which tend to leak air through the sealed areas. This occurs because opposed arcuate lengths of each film are gathered and sealed together in about the length of their common chord.